Toxocara vitulorum & Fasciola gigantica in cattle and buffalo in northern Laos

Abstract

LUZIA RAST – PhD THESIS… abstract Toxocara vitulorum & Fasciola gigantica in Cattle and Buffalo in Northern Laos In South-East Asia agricultural production including livestock is predominately produced within mixed smallholder farming systems. These mostly operate at subsistence levels. Cattle and buffalo are typically kept as assets rather than for optimal production purposes. Economic growth and urbanisation in the region continues to lead to increased demand for red meat products. This provides opportunities and pressures for smallholder farmers to increase their livestock outputs and supply this market with consistent and high quality products. Laos is well placed to supply this increasing regional demand but constraints inhibiting optimal production outputs from smallholder farming systems need to be addressed. These constraints include low capacity animal health systems, lack of infrastructure, traditional low input/low output farming methods and endemic livestock diseases. There is limited documentation about disease prevalence in large ruminants and basic production benchmarks such as reproductive, morbidity and mortality rates. Anecdotal reports indicate that Fasciola gigantica and Toxocara vitulorum are endemic in Laos and contribute to substantial production losses. This is despite the availability of relative cheap and simple treatment technology for T.vitulorum and substantial past research investment in the region on both parasites. The research presented in this thesis contributes to knowledge on the prevalence of T.vitulorum and F.gigantica in cattle and buffalo and the impact of these parasitic infections on production in mixed smallholder farming systems in northern Laos, which are typical for many other parts of South-East Asia. It further contributes to defining and documenting basic large ruminant production parameters within these production systems and quantifies the financial impact of T.vitulorum treatment of calves. Importantly this research identified a large gap in knowledge and in the sustained adoption of effective control practices for large ruminant internal parasites and explored pathways and gives recommendations to address this. The thesis presents data from seven separate field studies completed in northern Laos between 2009 and 2012. Two cross-sectional field surveys were conducted and results showed that both T.vitulorum in cattle and buffalo calves and F.gigantica in adult cattle and buffalo had high apparent prevalence (22.6% and 17.2% respectively) and were geographically widespread throughout northern Laos. Results further indicated that both parasites affected cattle and buffalo at similar levels and that no specific clinical signs were associated with either parasite. This was in line with past research on F.gigantica infection but not for T.vitulorum with limited past research and anecdotal reports indicating that Toxocariasis causes diarrhoea and rough coats in calves and especially so in buffalo calves. Slaughterhouse surveys were conducted in five main provincial slaughterhouses in northern Laos. Results showed a prevalence of faecal eggs for F.gigantica (34.1%) plus liver lesions consistent with F.gigantica infection in 71.0% of slaughtered cattle and buffalo providing further evidence of the endemic nature of this parasite and its potential clinical impact across northern Laos. Additional findings of the slaughterhouse surveys were that a large proportion of slaughtered female animals were pregnant (44% cattle, 47% buffalo), 9.8% of slaughtered animals had FMD lesions and meat inspectors were rarely present for the entire slaughter process with no condemnation of any products. Two separate farmer surveys on a sample of farmers that had their large ruminants tested for either T.vitulorum or F.gigantica were conducted using face-to-face semi-structured interviews. Results of the T.vitulorum farmer survey (n=273) showed that there was a relative high rate of awareness (62.3%) about this parasite amongst farmers and that specific knowledge about its epidemiology and potential clinical impact was lacking. Only 2.5% of farmers used pyrantel treatment of calves at the recommended age and dose rate. Results of the farmer survey (n=326) for F.gigantica showed smallholders had very limited knowledge about Fasciolosis in large ruminants despite 20.6% reporting having seen leaf shaped parasites in livers of slaughtered cattle or buffalo in the past. None of the interviewed farmers treated larger ruminants to control liver fluke. Analyses of large ruminant production data found annual calf morbidity and mortality rates of 42.6% (CI 0.38-0.47) and 37.3% (CI 0.33-0.42) respectively; and adult morbidity and mortality rates of 7.4% (CI 0.06-0.09) and 2.8% (CI 0.003-0.05) respectively. Further, results showed low reproductive performance of 0.6 and 0.4 calf per year for cattle and buffalo respectively with first calving ages of 36 months reported for both species. Two separate field treatment trials were conducted. For T.vitulorum calves were treated when they were <50 days old and results showed that locally produced and available pyrantel was effective, with a ≥95% reduction of T.vitulorum eggs in faeces four, eight and twelve weeks post treatment in cattle and buffalo calves compared to untreated calves of the same age. Results for imported triclabendazole oral drench and locally available triclabendazole/albendazole tablets manufactured in Vietnam, showed both produced >90% reduction of faecal egg counts in adult cattle and buffalo four, eight and twelve weeks post treatment compared to untreated animals. In addition there was a trend of increased weight gain in treated buffalo compared to the untreated control group indicating that treatment of Fasciolosis may result in heavier buffalo. Financial analysis using partial budgeting and data from our surveys showed that there was a large net benefit of USD 3.69-14.86 per calf for treatment with pyrantel (12.5 mg/kg) once only between 14-21 days of age compared to no treatment. It was concluded that both T.vitulorum and F.gigantica are endemic in northern Laos and contribute to substantial production losses in this area. Smallholder farmers still keep large ruminants mostly as an asset and there is also a large knowledge gap amongst smallholder producers about internal parasites, their health and production effects and effective control methods. This knowledge gap and the lack of commercial driver contribute to the deficit of widespread adoption of parasite control methods by smallholder farmers despite their availability and known effectiveness. These results suggest, especially for T.vitulorum that if recommended control methods were widely adopted, large ruminant production output from smallholder farming systems could be increased through reduced calf morbidity and mortality rates.